Electrostatic discharge (ESD) is the sudden and momentary electric current that flows between two objects at different electrical potentials caused by direct contact or induced by an electrostatic field. ESD is a serious issue in solid state electronics, such as integrated circuits (IC) and power transistors made from semiconductor materials such as silicon and insulating materials such as silicon dioxide. Either of these materials can suffer permanent damage when subjected to high voltages; as a result, there are now a number of antistatic devices that help prevent static build up.
On-chip ESD protection circuits with various diode structures have also been developed. With the shallower junction, much thinner gate oxide, salicide (self-aligned silicided) diffusion, Cu inter-connection and LLD (Light-Doped Drain) structure used on the MOSFET devices, ESD issue has become a main reliability concern of CMOS integrated circuits in sub-quarter-micron CMOS technology. To sustain a reasonable ESD stress for safe mass production, on-chip ESD protection circuits have to be added into the IC products.
Conventional power MOSFET devices with ESD protection circuits have also been developed. The ESD protection circuit diverts the ESD safely away from the rest of the MOSFET device. Conventional power MOSFET devices with ESD protection circuits generally have a layout and layer structures that require application of seven masks in typical manufacturing processes. These seven masks include a trench mask, an ESD mask, a body mask, a source mask, a contact mask, a metal mask and a passivation mask. With the seven masks required in the manufacturing processes, the processing steps are more complicated and time consuming In addition, the conventional method involves forming an additional poly layer above the silicon surface. Therefore, it may require additional poly deposition and two additional masks to pattern and form P-N junctions for the ESD structure. This adds cost and time in terms of extra masks and extra layers and extra steps. In addition, lithography machines and photoresists are expensive. The ESD protection circuit diverts the ESD safely away from the rest of the MOSFET device.
It is within this context that embodiments of the present invention arise.